1. Field of the Invention
The present invention relates generally to a read head for a hard disk drive, and more particularly to a giant magnetoresistance (GMR) read head including a GMR read sensor in a read region and stitched longitudinal bias (LB) stacks in two side regions.
2. Description of the Prior Art
In a commonly used giant magnetoresistance (GMR) read head, a GMR read sensor is located in a read region, while a longitudinal bias (LB) stack and a conductor are located in each of two side regions. The GMR read sensor typically comprises nonmagnetic seed layers, an antiferromagnetic pinning layer, ferromagnetic pinned layers, a nonmagnetic spacer layer, a ferromagnetic sense layer, and nonmagnetic cap layers. The LB stack typically comprises a nonmagnetic seed layer and a hard-magnetic LB layer. The conductor typically comprises highly electrically conducting nonmagnetic layers.
The LB layer must exhibit a high coercivity (HC) and thus provide an LB field for stabilizing the sense layer. This stabilization scheme is the most effective when the midplane of the LB layer is located at the same horizontal level as the midplane of the sense layer. In the prior art head fabrication process, however, the LB stack is typically deposited on an amorphous Al2O3 bottom gap layer in the side regions to prevent some unwanted microstructural effects that causes a decrease in HC, and thus the midplane of the LB layer is located at a horizontal level significantly lower than the midplane of the sense layer. As a result, it is difficult to stabilize the sense layer.
There is therefore a need for a head fabrication process in which the LB layer can exhibit a high HC and its midplane can be located at the same horizontal level as the midplane of the sense layer, so that the most effective stabilization of the sense layer can be obtained.